Tag Archives: Universe

Scientists have been able to recreate the entire Universe inside a computer for the first time ever. A simulation running on a supercomputer, tracking a mind boggling 550 billion particles as they evolve, has been able to recreate the structure of the Universe right from the Big Bang to the present day.

Simulating the Standard Model of Cosmology

This is the first in the series of three simulations to be carried out on GENCI’s new supercomputer, CURIE at CEA’s TGCC (Tres Grand Centre de Calcul) performed by researchers from Laboratoire Univers et Theorie (LUTH). This takes into account the standard model of cosmology with the cosmological constant built in. Successive runs will improve upon this result with more data, especially about the distribution of dark matter and dark energy. The project, called Deus: full Universe run, will seek answers to the cosmological questions in a way similar to what the LHC follows in order to get answers.

Why simulation?

The physics at the LHC is massively complicated by the presence of so many particles and so many end states of a certain collision. It is impossible to analytically solve for the end state, so scientists use models before they begin an experiment. These simulations reveal what the most likely result of a certain collision is given certain parameters and bounds on certain numbers. The actual run either confirms the simulation, or discards it. This is a far more efficient process than reconstructing the interaction by looking at the end states, which is the other alternative.

The Deus simulation does something like that. They let the 550 billion points evolve and see what the end state is. This has enabled them to count the number of galaxy clusters which are more massive than a hundred thousand billion solar masses (that’s VERY heavy, by the way) and the number comes out to be 144 million. The first galaxy cluster formed 2 billion years after the Big Bang, according to the simulation. It also shows the most massive galaxy cluster – with a mass of 15 quadrillion (or 15 thousand trillion) solar masses!

Relics of the Early Universe

The simulation also revealed fingerprints of the inflationary era in the form of fluctuations in the Cosmic Microwave Background Radiation. If the Big Bang and inflation is true, then there must be radiation left over, which is constantly weakening. This permeates all of the space in the Universe, thus the name Cosmic Microwave Background (CMB). It is believed that some quantum fluctuation, growing under the effect of gravity, gave rise to the galaxy and clusters we see today. The CMB was studied thoroughly by the WMAP studies. They also showed up in the simulation.

Where are we? That dot - that single dot - is the entire Milky Way!

The simulation also confirmed the presence of dark matter and gave a hint of how it might be distributed throughout the Universe. Present in this primordial virtual cosmic soup is the Baryon Acoustic Oscillations or BAO. This might be the answer to the long standing problem of baryon asymmetry – why matter outnumbers anti-matter in the Universe, whereas they should have been produced in equal numbers in the Early Universe.

Computing power – the sky is the limit

CURIE is one of the largest supercomputer facilities in the world. The whole simulation has taken a few years to put together. The whole project is expected to use more than 30 million hours (or 3500 years) of computing time on all CPU’s of CURIE. The amount of data processed comes out to be 150 PB (peta bytes). This amounts to all the data on 30 million DVD’s. State-of-the-art compression technology has allowed researchers to reduce this entire jungle to 1 PB.

Future

Two more simulations are to follow! They will test out rival cosmological models. The simulation is also expected to reveal structures we have not been familiar with before. This will provide scientists a search parameter for current projects like PLANCK and future ones like EUCLID.

The grand old man of Physics is proved right once again. Albert Einstein was vindicated yet again by a survey, which confirmed the presence of Dark Energy in the Universe. The ‘WiggleZ Dark Energy Survey’ was conducted by 26 astronomers from 14 countries using the latest in spectrograph technologies to map out more than 200,000 galaxies, many halfway across the Universe to confirm this startling fact.

What is Dark Energy?

Dark Energy is the name given to the unknown entity believed to be behind the acceleration of the expansion of the Universe. It was Edwin Hubble, who in 1932, first noticed that the Universe was actually expanding. This gave a huge boost to the Big Bang theory, which says that the Universe came out of an ultra-dense singularity 14-15 billion years ago. Scientists have been expecting the expansion to slow down as time wears on, as then gravity will eventually dominate. What scientists found, instead, was that the Universe was expanding at an ever-increasing rate. It is believed that some mysterious source of energy was aiding the expansion process, thus named Dark Energy.

No one has come up with a proper explanation of Dark Energy, despite there being a number of hypotheses and models. Dark Energy supposedly makes up 73% of the Universe, Dark Matter 23 % (which is NOT the same as Dark Energy; Dark Matter slows down the expansion) and the rest 4% – is ordinary matter – stars, galaxies, nebulae and super-clusters.

Where Einstein fits in…

Einstein had almost predicted the expansion of the Universe in his Theory of General Relativity, but in an uncharacteristic situation in which his nerves weakened, he introduced a factor in his equations which predicted a static Universe. This amounted to including in his equations, a cosmological constant a ‘fudge factor’ which gives vacuum a repelling force, effectively enabling the Universe to counter its own gravity and preventing self-collapse. Later, Einstein would rue this as his ‘greatest blunder’. Now, it seems that the great man was not wrong!

Inflationary theories of modern cosmology use this idea of a cosmological constant to explain the supposed period of rapid expansion right after the Big Bang called inflation. Now, with the increasing rate of expansion, it seems that the cosmological constant was the genius’ masterstroke rather than a botch-up.

The WiggleZ survey

The WiggleZ survey, conducted by an Australian-based group led by Dr. Michael Drinkwater, used the latest in spectrography, thanks to latest Australian technology to survey galaxies more than 200000 of them some 7 billion light years away. Light takes a finite time to travel from one place to another, because of its finite speed. Thus the light from 7 billion light years away took 7 billion years to reach here. This means that we are seeing galaxies in the form they were 7 billion years ago, essentially looking back in time! (Thus, the easiest way to glance into the past is to just see. The farther away the object you see, the farther away in time it is!). The WiggleZ survey can map 392 galaxies in an hour!

Do Structures such as these give clues to Dark Matter and Energy?

Though, this doesn’t tell us the constituents of Dark Energy (or Dark Matter, which is also a mystery), it gives definitive confirmation of its existence. It gives scientists confidence that Einstein’s theory is not failing, and that Dark Energy can indeed be reconciled with General Relativity. The survey is exhaustive measuring both the pattern of distribution of galaxies in the Universe and the rate of formation of the galaxy clusters, essentially giving scientists a two-way confirmatory proof of Dark Energy.

So, there it is again! Einstein is proved right again, and in spectacular fashion. 96% of the stuff in the Universe is unknown, but at least we know that it’s there. Some consolation and a lot of work to be done!

A radical new notion might kill nearly all inconsistencies in modern physics and cosmology in one fell swoop. Prof. Dejan Stojkovic, assistant physicist at Buffalo University and team has proposed the startling hypothesis that the nascent Universe may have had just one dimension. They suggest that the Universe begins to grow’ dimensions as it expands and cools.

What exactly is the hypothesis?

The Big Bang theory suggests that the Universe began from an infinitesimal point and then expanded rapidly in all directions and in time. This new hypothesis would mean that the early Universe expanded in a straight line, and then into a plane and then into the three dimensions we see today.

The radical idea further suggests that as the energy density of the Universe falls (i.e. the Universe cools), more dimensions open up. A fourth spatial dimension might have already opened up at cosmological scales, opines Stojkovic.

Prof. Dejan Stojkovic

The team even suggests a test to verify this hypothesis. Since gravitational waves exist only in three spatial dimensions, they could not have existed in the very early Universe. Data from Laser Interferometer Space Antenna (LISA) should not detect any gravitational waves from that time. Since looking deeper in the Universe represents going further back in time, analyzing light from very far away should give verification.

However, gravitational waves are extremely hard to detect owing to their extremely small theoretical magnitude. Further, this is a negative test, which is not very good for a theory. The gravitational waves might just be there, but may be too feeble to detect.

How does this resolve inconsistencies?

Stojkovic claims that this notion may remove the incompatibility between quantum mechanics and general relativity. The idea might even solve the mystery of the accelerating expansion of the Universe. Stojkovic claims that addition of new dimensions would explain the accelerating expansion.

All that can be said about this idea is that it is radical, but untested. Many radical and beautiful ideas have gone out of the window, after failing to stand up to experimental tests. If it disagrees with experiment, it’s wrong.